I'm facing a related problem: how to keep my PIC powered long enough in the
absence of line power. I bought a couple of super caps (5V, 1.5 F)
originally to power a clock chip that was designed for this. But I've moved
the clock functionality into the PIC (a 16F877), so now I need to keep power
to the PIC.

I think what I'll do is find a way for the PIC to monitor main power, and
then just go into sleep if that falls below some level. The super cap can
probably be wired straight to Vdd with steering diodes to keep it from
powering the rest of the circuit. Then I'll wire RB0/INT to the supply
outside the diode, and if that level falls from high, it can generate an
interrupt to execute code to handle sleep.

>
> on 3/13/01 6:14 AM, Byron A Jeff at byronKILLspamCC.GATECH.EDU wrote:
>
> > I'm open to any other ideas.
>
> I'm facing a related problem: how to keep my PIC powered long enough in the
> absence of line power. I bought a couple of super caps (5V, 1.5 F)
> originally to power a clock chip that was designed for this. But I've moved
> the clock functionality into the PIC (a 16F877), so now I need to keep power
> to the PIC.
>
> I think what I'll do is find a way for the PIC to monitor main power, and
> then just go into sleep if that falls below some level. The super cap can
> probably be wired straight to Vdd with steering diodes to keep it from
> powering the rest of the circuit. Then I'll wire RB0/INT to the supply
> outside the diode, and if that level falls from high, it can generate an
> interrupt to execute code to handle sleep.
>
> I, too, would appreciate any comments.

Well first off I'd run a couple of tests and see how long the supercap
drives the 16F877. Honestly the difference between sleep and not sleep isn't
much.

> on 3/13/01 6:14 AM, Byron A Jeff at .....byronKILLspam.....CC.GATECH.EDU wrote:
>
> > I'm open to any other ideas.
>
> I'm facing a related problem: how to keep my PIC powered long enough in the
> absence of line power. I bought a couple of super caps (5V, 1.5 F)
> originally to power a clock chip that was designed for this. But I've moved
> the clock functionality into the PIC (a 16F877), so now I need to keep power
> to the PIC.
>
> I think what I'll do is find a way for the PIC to monitor main power, and
> then just go into sleep if that falls below some level. The super cap can
> probably be wired straight to Vdd with steering diodes to keep it from
> powering the rest of the circuit. Then I'll wire RB0/INT to the supply
> outside the diode, and if that level falls from high, it can generate an
> interrupt to execute code to handle sleep.
>
> I, too, would appreciate any comments.
>
> ------------------------------------------------------------
> Roderick Mann EraseMErmannspam_OUTTakeThisOuTlatencyzero.com.sansspam
>
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